Batch Update HTML Files?

I am a bit new to the Mac world and have finally ditched my last Windows PC. I have gone to edit my web page and cannot figure out how to batch update all my HTML files at once.

All my HTML files have the same side bar, header, and footer. Sometimes those need to be changed (which would cause that change on ALL the HTML files).

On my windows machine, my HTML editor had a function where I could do a find and replace of all HTML files in a directory. Is there any way to do that on a Mac? Free SW would be nice but I know that isn't always the case.

If you plan on working on websites with HTML, I'd highly recommend Rage Web Design. I've tried all of the HTML editors, and Web Design is, in my opinion, the best with the most features. And it's reasonably priced.